Does the Bible say that if you have broken one commandment you have broken them all?

For whoever keeps the whole law but fails in one point has become accountable for all of it. {11} For he who said, “Do not commit adultery,” also said, “Do not murder.” If you do not commit adultery but do murder, you have become a transgressor of the law.

Indeed, if we do not love our neighbour as ourself (James 2:8-9) then we are breaking the whole law. John puts it like this:

Everyone who makes a practice of sinning also practices lawlessness; sin is lawlessness. (1John 3:4)

Even though Christians don’t need to keep the Law any more (Rom. 10:4), if we sin we are law breakers. This is to encourage us to try to live a life like God’s: a life away from sin; a life of love towards others, because God is love (1John 4:8,16).

Thankfully, when we sin God is willing to forgive us if we repent (1John 1:9). Part of the purpose of the Law was to help us realise that they couldn’t be righteous without faith in God’s grace to forgive (Gal.3:19-24); we are reminded of this when we fail to love our neighbour as ourselves, and we can continue to rely on God’s grace to forgive us.